dylee8 Loc: South Florida

I got my new Nikon 28-300mm lens. As a comparison I took my other 2 lenses with 300mm - Nikon 55-300, and Sigma 150-600, and took the 3 pictures, all at 300mm, mounted on my D7000.

The pictures here, all uncropped, show that even all at 300mm, taken from the same spot, they zoomed differently.

First picture 28-300, second 55-300, third 150-600

Did I do something wrong? Or is there a more complicated way to convert focal length to zoom factor? Thanks

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donrent Loc: Punta Gorda , Fl

To me,your new lens need to go back for a refund........

legion3 Loc: Deer Park Long Island

they are out of focus

imagemeister Loc: mid east Florida

Were they all taken from exactly the same distance and same aperture ??

Apaflo Loc: Anchorage, Alaska

Generally most zooms are only relatively close to the long focal length they are advertised as. Hence we might suspect that a 150-600mm lens would be very close to 300mm at the marked 300mm, but that the other two may be anything from 270mm to 310mm, and most likely would be about 285mm (5% low).

Another thing to expect is that a zoom lens will not likely be anywhere near as sharp at the upper limit of its focal length range as it will be in the center. Therefore the 150-600mm should be expected, at 300mm, to produce noticeably sharper images.

On the flip side of the coin, a 150-600mm will be much larger and heavier, and will probably cost more.

There are always ups and downs to using otherwise "equivalent" lenses!

oldtigger Loc: Roanoke Virginia-USA

Were the lenses focused at less than infinity?
It makes a large difference on some lenses

donrent Loc: Punta Gorda , Fl

Another point: flowers are NOT the best subject to use for a lens "showoff"...

Apaflo Loc: Anchorage, Alaska

Focus is fine.

They are all shot at 300mm. The first one at 1/40 and the last two at 1/50 shutter speed. An appropriate shutter speed to get a sharp picture would have been 1/500; or if VR is expected to work it has to be enabled for about 1/2 second before the shutter fires to give it time to stabilize.

dylee8 Loc: South Florida

Yes they were. In fact because the 150-600 is much longer I had to move back 6 inches.

dylee8 Loc: South Florida

The lenses are focused at around 12 feet, where I placed the camera.

Apaflo Loc: Anchorage, Alaska

That is a good point! The Exif data says 3.3m, 3.5m and 3.7m, so they are all basically shot at 10+ feet and the focal length is probably not close to 300mm for any of them.

imagemeister Loc: mid east Florida

Yes, zooms at that close a distance will vary widely as to FOV

dylee8 Loc: South Florida

That can probably explain why. But the Exif also says 300mm.

Apaflo Loc: Anchorage, Alaska

But that refers focal length defined as the distance of the lens from the sensor when focused at infinity.

When not focused at infinity, focal length is actually an "effective focal length". And how that is affected by focus distance depends on the lens design. Up until 25 years or so ago lenses focused closer by moving the entire lens away from the sensor. But now almost all lenses use what is called an Internal Focus design, which has a fixed distance to the sensor and instead moves internal groups of elements in relation to each other.

One effect, most noticed when neither the front or back elements of the lens moves, is that the effective focal length becomes much shorter as the minimum focus distance is approached.

Which is to say, your 300mm lens is close to 300mm when focused on the moon, but it might be only 200mm when focused as close as it can. Or 220, or 250mm... each might be very different! But that is what allows a 12 foot minimum focus distance rather than only 20 feet.

The significance is that there is nothing wrong with any of your lenses in the sense that at one set focus distance they all exhibit different effective focal lengths. It is very much to be expected.

dylee8 Loc: South Florida

Thank you very much Apaflo.

Explanations like this is what makes UGH so helpful.